In-cell NMR spectroscopy has recently emerged as a unique source of atomically resolved information on the structure, dynamics, and interactions of nucleic acids (NAs) within the intracellular space of living cells. Its recent applications have helped reveal fundamental differences in the behaviour of NAs in cells compared to the in vitro conditions commonly used for their study, as well as in physiologically distinct cellular states. This review covers the fundamental principles and practical aspects of acquiring in-cell NMR data in currently established eukaryotic cellular models, Xenopus laevis oocytes, and human cells. The primary purpose of this review is to present and discuss the technical and conceptual aspects of in-cell NMR sample preparations and their manipulations during in-cell NMR data acquisition, as understanding these aspects is vital for comprehending the physiological significance of in-cell NMR data and the information they provide. Considerations on the planning of in-cell NMR experiments and the presentation of in-cell NMR data on nucleic acids are discussed. We hope this will enable readers to navigate through the ever-growing pool of in-cell NMR literature and gain the knowledge needed to assess and comprehend published data independently. Additionally, we hope it will inspire some readers to actively participate in this rapidly expanding and fascinating field of cellular structural biology.